Structural effects on intermediate species of methanol oxidation are studied on low-index planes of platinum using in-situ infrared (IR) spectroscopy. A flow cell is designed for rapid migration of reactant and product species on the electrode surface. IR spectra show adsorption of formate and the formation of carbonate species on the Pt(111) surface at potentials higher than that of CO oxidation. The band assignments for carbonate and formate are confirmed by vibrational isotope shifts. On Pt(100), the absorption band of adsorbed formate is much smaller than that on Pt(111). On the other hand, there is no adsorbed formate on Pt(110) in the potential region examined. The band intensity of formate follows the order: Pt(111)>Pt(100)>Pt(110). This order is opposite to that of the current density in the regions of higher potential. Adsorbed formate on Pt(111) behaves like a catalyst-poisoning intermediate, like adsorbed CO.